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Full text of "Text Book Of Mechanical Engineering"

Appendix II.

907

water B, and covered by a combustion chamber c having holes
for escape of gas. E is a thermometer, and F a cock for the first
rush of gas when testing, but otherwise shut. The method of
use is to weigh a small quantity of dry powdered fuel, and with
it the necessary amounts of potassic chlorate and potassium
nitrate to produce complete combustion. These are next placed
in vessel A, the fuse lighted, covered with vessel c, and the
whole immersed in a known weight of water B. The fuel
gradually burning, heat is given to the water, whose tem-
perature is raised, and it is then a simple matter to find the
B.T.U. per Ib. of fuel. (See f. 1148.)

Liquid Fuel, commonly the residue 'astatki' due to, the
distillation of lighter oils from petroleum, is more used than
formerly. The method now adopted is to induce and inject the
oil as spray, by means of a steam jet, and the system has many
advantages, such as very complete combustion, absence of stoking,
one-third less chimney-heat loss compared with coal and twice the
evaporative value, as well as a further increased evaporation for
the same grate area through decreased dilution of the gases.
A good 'sprayer' should give fine spray, little noise, and be
quickly separable for cleaning, which requirements are well met
(according to Mr. R. Wallis in his N.E. Coast Inst. paper, from .
which these notes are taken) by the Rusden and Eeles apparatus,
Fig, 869. Both oil and steam jets are annular and regulated by
hand wheels, and the complete installation, Fig. 870, consists of
a pump A to raise the oil to a service tank B, thence to the
sprayers, a steam pipe c for the oil feed-pump A, and another D
for the sprayers, the steam being superheated on its way to secure
higher efficiency and economy. The furnaces are partially lined
with firebrick to distribute the heat, and to retain it for some time
after the jet is extinguished. Before lighting, the furnace should
be blown out by steam, and the torch applied before turning on
the spray, otherwise an explosion is possible.

P. 698. Artificial Draught.—Forced Draught has already
been explained in principle. It is practised in three different
ways. The closed stokehold, with air from fans under a water
head of £", and air-locks for the passage of stokers, is still in
operation with economical results, and without apparent injury to